The Tea Party Express, in a new email to supporters, crowned Sen. Thad Cochran (R-MS), the most "vulnerable of the old GOP senators" who's likely to go the way of former Sen. Dick Lugar (R-IN).

The scathing new fundraising email on Saturday came a few days after another prominent tea party group, Tea Party Patriots, endorsed Cochran's tea party primary challenger, state Sen. Chris McDaniel (R-MS). Tea Party Express groups Cochran with a number of other Republican senators as as Republicans In Name Only (RINO).

"While many of the RINO Republican U.S. Senators that are in the cross-hairs of their more conservative Republican primary challengers have tried to shore-up their right flank by at least trying to portray an image that they are conservative, Senator Cochran has not followed that savvy political strategy," the email read.

Tea Party organizations have been aggressively attacking Cochran for saying that he didn't know a lot about the tea party. Tea Party Express went on to compare Cochran to Lugar, who was defeated by Indiana state Treasurer Richard Mourdock in the 2012 GOP Senate primary before Mourdock went on to lose to now Sen. Joe Donnelly (D-IN) in the general election.

"Instead, he has remained defiant and even dismissive of the Tea Party movement," the email continued. "This strategy didn't work for former Senator Dick Lugar of Nebraska, and it will not work for Senator Cochran!"

A number of incumbent Republicans have been made to watch their right flank this cycle due to tea party challenges, among them Senate Minority Leader Mitch McConnell (R-KY) and Sen. Pat Roberts (R-KS).

"He is a true Tea Party conservative firebrand cut from the same cloth as Ted Cruz, Mike Lee, and Rand Paul," the email read. "The aforementioned have served us admirably, but it is clear that they need reinforcements. "